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  • Counting down to zero in contrast to counting up to length - 1

    - by Helper Method
    Is it recommended to count in small loops (where possible) down from length - 1 to zero instead of counting up to length - 1? 1.) Counting down for (int i = a.length - 1; i >= 0; i--) { if (a[i] == key) return i; } 2.) Counting up for (int i = 0; i < a.length; i++) { if (a[i] == key) return i; } The first one is slightly faster that the second one (because comparing to zero is faster) but is a little more error-prone in my opinion. Besides, the first one could maybe not be optimized by future improvements of the JVM. Any ideas on that?

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  • creational pattern for instances depending on multiple subclass instances

    - by markusw
    I have a problem, for that I was not able to identify a suitable design pattern. I want to create instances depending on a given type that has been passed to a factory method. What I am doing until now is the following: T create(SuperType x) { if (x instanceof SubType1) { // do some stuff and return a new SubType extends T } else if (x instanceof SubType2) { // do some stuff and return a new SubType extends T } else if ... } else { throw new UnSupportedOperationException("nothing defined for " + x); } } It seems not to be best pratice for me. Has anybody an idea how to solve this in a better way?

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  • How to get a Class literal from a generically specific Class

    - by h2g2java
    There are methods like these which require Class literals as argument. Collection<EmpInfo> emps = SomeSqlUtil.select( EmpInfo.class, "select * from emps"); or GWT.create(Razmataz.class); The problem presents itself when I need to supply generic specific classes like EmpInfo<String> Razmataz<Integer> The following would be wrong syntax Collection<EmpInfo<String>> emps = SomeSqlUtil.select( EmpInfo<String>.class, "select * from emps"); or GWT.create(Razmataz<Integer>.class); Because you cannot do syntax like Razmataz<Integer>.class So, how would I be able to squeeze a class literal out of EmpInfo<String> Razmataz<Integer> so that I could feed them as arguments to methods requiring Class literals? Further info Okay, I confess that I am asking this primarily for GWT. I have a pair of GWT RPC interface Razmataz. (FYI, GWT RPC interface has to be defined in server-client pairs). I plan to use the same interface pair for communicating whether it be String, Integer, Boolean, etc. GWT.create(Razmataz) for Razmataz<T> complains that, since I did not specify T, GWT compiler treated it as Object. Then GWT compiler would not accept Object class. It needs to be more specific than being an Object. So, it seems there is no way for me to tell GWT.create what T is because a Class literal is a runtime concept while generics is a compile time concept, Right?

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  • Cast object to interface when created via reflection

    - by Al
    I'm trying some stuff out in Android and I'm stuck at when trying to cast a class in another .apk to my interface. I have the interface and various classes in other .apks that implement that interface. I find the other classes using PackageManager's query methods and use Application#createPackageContext() to get the classloader for that context. I then load the class, create a new instance and try to cast it to my interface, which I know it definitely implements. When I try to cast, it throws a class cast exception. I tried various things like loading the interface first, using Class#asSubclass, etc, none of which work. Class#getInterfaces() shows the interface is implemented. My code is below: PackageManager pm = getPackageManager(); List<ResolveInfo> lr = pm.queryIntentServices(new Intent("com.example.some.action"), 0); ArrayList<MyInterface> list = new ArrayList<MyInterface>(); for (ResolveInfo r : lr) { try { Context c = getApplication().createPackageContext(r.serviceInfo.packageName, Context.CONTEXT_IGNORE_SECURITY | Context.CONTEXT_INCLUDE_CODE); ClassLoader cl = c.getClassLoader(); String className = r.serviceInfo.name; if (className != null) { try { Class<?> cls = cl.loadClass(className); Object o = cls.newInstance(); if (o instanceof MyInterface) { //fails list.add((MyInterface) o); } } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } // some exceptions removed for readability } } catch (NameNotFoundException e1) { e1.printStackTrace(); }

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  • What is the relation between ContentPane and JPanel?

    - by Roman
    I found one example in which buttons are added to panels (instances of JPanel) then panels are added to the the containers (instances generated by getContentPane) and then containers are, by the construction, included into the JFrame (the windows). I tried two things: I got rid of the containers. In more details, I added buttons to a panel (instance of JPanel) and then I added the panel to the windows (instance of JFrame). It worked fine. I got rid of the panels. In more details, I added buttons directly to the container and then I added the container to the window (instance of JFrame). So, I do not understand two things. Why do we have two competing mechanism to do the same things. What is the reason to use containers in combination with the panels (JPanel)? (For example, what for we include buttons in JPanels and then we include JPanels in the Containers). Can we include JPanel in JPanel? Can we include a container in container?

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  • How to get current compass reading android 2.1

    - by Brandon Delany
    How do I get the current compass reading in android 2.1? I know that I can initiate a listener and receive updates but I do not need constant updates I only need it to get the compass orientation when the user clicks a button. Also what is the most accurate way to get the compass orientation? Lastly, how do I send fake data to the android console. I know that you're supposed to use the terminal and send it commands but what are the commands I can't seem to find it on the Android website. Thank you

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  • Trying to create spring project with maven

    - by Gandalf StormCrow
    Hello everyone I was just going trough http://static.springsource.org/docs/Spring-MVC-step-by-step/part1.html spring tutorial, and I thought its old I'll think something better on my own. For starters how do I start spring project with maven, which archtype should I choose? I wanna create simple spring app, write class which I will deploy to jboss, spring will instansiate it at startup .. that is what have in mind for now .. for now I need to start it first

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  • Checked equivalent to IllegalArgumentException?

    - by jv1975oid
    I have a method that takes an enum as a parameter and returns some information dependent on that parameter. However, that enum contains some values which should not be handled, and should raise an error condition. Currently the method throws an IllegalArgumentException but I would like this to be a checked exception to force callers to catch it (and return gracefully, logging an error). Is there something suitable or should I create my own Exception subclass? I'm open to other patterns as well. A reasonable reaction would be that all values of the enum should be handled, but that isn't the case. When a new value is added to the enum, I want to make sure that this method does the right thing - alerting a human is preferable to using some default return value in this case. Thanks for any advice.

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  • Attributes in XML subtree that belong to the parent

    - by Bart van Heukelom
    Say I have this XML <doc:document> <objects> <circle radius="10" doc:colour="red" /> <circle radius="20" doc:colour="blue" /> </objects> </doc:document> And this is how it is parsed (pseudo code): // class DocumentParser public Document parse(Element edoc) { doc = new Document(); doc.objects = ObjectsParser.parse(edoc.getChild("objects")); for ( ...?... ) { doc.objectColours.put(object, colour); } return doc; } ObjectsParser is responsible for parsing the objects bit, but is not and should not be aware of the existence of documents. However, in Document colours are associated with objects by use of a Map. What kind of pattern would you recommend to give the colour settings back to DocumentParser.parse from ObjectsParser.parse so it can associate it with the objects they belong to in a map? The alternative would be something like this: <doc:document> <objects> <circle id="1938" radius="10" /> <circle id="6398" radius="20" /> </objects> <doc:objectViewSettings> <doc:objectViewSetting object="1938" colour="red" /> <doc:objectViewSetting object="6398" colour="blue" /> </doc:objectViewSettings> </doc:document> Ugly!

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  • ExecutorService that interrupts tasks after a timeout

    - by scompt.com
    I'm looking for an ExecutorService implementation that can be provided with a timeout. Tasks that are submitted to the ExecutorService are interrupted if they take longer than the timeout to run. Implementing such a beast isn't such a difficult task, but I'm wondering if anybody knows of an existing implementation.

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  • Using thread inter-communication to increase my server app's IO throughput; not sure how

    - by Howard Guo
    My server application creates a new thread for each incoming connection. Incoming requests are serialized in a BlockingQueue. There is one worker thread taking items from the queue, produce a response and send the response through socket. I have noticed a throughput issue: Currently, worker thread is responsible of sending the response message through socket, thus severely wasting processing power and throughput. I am considering: rather than sending the response itself, why not telling network IO threads to send the response? However, when I think about thread inter-communication, I cannot yet figure out how to approach it: Worker thread will produce a response, but how will it inform the response message to IO thread? Is there a standard/best practice? Thank you.

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  • What web UI framework is most suitable for building dynamic pages / forms?

    - by waxwing
    Hello, We are at a stage where we are considering different Web UI frameworks (most likely component based ones such as GWT, JSF, Wicket, Vaadin, etc). One of the main use cases / constraints is that it must support generating dynamic pages. I.e., the page/form layout and components is stored in a database and is changeable at runtime, and from this pages are generated. We are also going to write static layouts, but that is not the main focus of this question. I thought maybe the user community here can share experiences of different frameworks in this context. Are there differences in ease of implementation and what is suitable?

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  • How to create new account using servlets

    - by Alvin
    I want to know how can I create new account using servlets in post method? I'm currently following MVC design pattern, and I want to know if I pass the required data to register new account from JSP page, then how can I get that data in post method? As request.getParameter() method returning me null. How can I know that post method is calling to create new account? How can I pass all the relevant user information from servlets to model class for registering data to the database table?

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  • richfaces keepAlive not working

    - by Jurgen H
    I have a mediaOutput tag which, in its createContent attribute, requires the backing bean to be in a certain state. A list of values, which is filled in an init method, must be available. I therefore added a keepAlive tag for the whole backing bean. I now indeed see the backingBean in stead of some (richfaces) proxy bean, but the filled list is null again. How to make this possible? I checked that the init method was called and that the list is filled in in the init method. <a4j:keepAlive beanName="myBean" /> <a4j:mediaOutput createContent="#{myBean.writeChart}" ... /> The backing bean public class MyBean implements Serializable { public List list; public void init(ActionEvent event) { // call some resource to fill the list list = service.getItems(); } public void writeChart(final OutputStream out, final Object data) throws IOException { // list is null } // getters & setters }

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  • NetBeans config file

    - by Ockonal
    Hi guys, my NetBeans has ugly fonts in interface. I'm going to make antialiasing for it. In internet I saw that there is should be -J-Dswing.aatext=true -J-Dawt.useSystemAAFontSettings=on in netbeans_default_options. This file should be located in /etc/netbeans.conf. But there isn't this file. I have NetBeans 6.8. Help, please.

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  • Blackberry XML Parsing Application not working

    - by Nirmal
    Hello All... I found one sample application from the Blackberry knowledgebase. From that application I have put that sample application on my eclipse plugin, and the code is as follows : import javax.microedition.io.*; import net.rim.device.api.ui.*; import net.rim.device.api.ui.component.*; import net.rim.device.api.ui.container.*; import net.rim.device.api.system.*; import net.rim.device.api.xml.parsers.*; import org.w3c.dom.*; import org.xml.sax.*; class XML_Parsing_Sample extends UiApplication { // creating a member variable for the MainScreen MainScreen _screen = new MainScreen(); // string variables to store the values of the XML document String _node, _element; Connection _connectionthread; public static void main(String arg[]) { XML_Parsing_Sample application = new XML_Parsing_Sample(); // create a new instance of the application // and start the application on the event thread application.enterEventDispatcher(); } public XML_Parsing_Sample() { _screen.setTitle("XML Parsing");// setting title _screen.add(new RichTextField("Requesting.....")); _screen.add(new SeparatorField()); pushScreen(_screen); // creating a screen // creating a connection thread to run in the background _connectionthread = new Connection(); _connectionthread.start();// starting the thread operation } public void updateField(String node, String element) { // receiving the parsed node and its value from the thread // and updating it here // so it can be displayed on the screen String title = "My App"; _screen.add(new RichTextField(node + " : " + element)); if (node.equals(title)) { _screen.add(new SeparatorField()); } } private class Connection extends Thread { public Connection() { super(); } public void run() { // define variables later used for parsing Document doc; StreamConnection conn; try { // providing the location of the XML file, // your address might be different conn = (StreamConnection) Connector .open("http://www.sufalamtech.com/demo/moviewebservice/Test.xml"); // next few lines creates variables to open a // stream, parse it, collect XML data and // extract the data which is required. // In this case they are elements, // node and the values of an element DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory .newInstance(); DocumentBuilder docBuilder = docBuilderFactory .newDocumentBuilder(); docBuilder.isValidating(); doc = docBuilder.parse(conn.openInputStream()); doc.getDocumentElement().normalize(); NodeList list = doc.getElementsByTagName("*"); _node = new String(); _element = new String(); // this "for" loop is used to parse through the // XML document and extract all elements and their // value, so they can be displayed on the device for (int i = 0; i < list.getLength(); i++) { Node value = list.item(i).getChildNodes().item(0); _node = list.item(i).getNodeName(); _element = value.getNodeValue(); updateField(_node, _element); }// end for }// end try // will catch any exception thrown by the XML parser catch (Exception e) { Dialog.alert("exception = " + e); } }// end connection function }// end connection class }// end XML_Parsing_Sample But when I am running this application, the simulator just showing me a Blank screen with label Requesting... Anybody help me out for this ? Thanks in advance...

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  • Change ListView background - strage behaviour

    - by Beasly
    Hi again, I have a problem with changing the background of a view in a ListView. What I need: Change the background image of a row onClick() What actually happens: The background gets changed (selected) after pressing e.g. the first entry. But after scrolling down the 8th entry is selected too. Scroll back to the top the first isn't selected anymore. The second entry is selected now. Continue scrolling and it continues jumping... What i'm dong in the Code: I have channels, and onClick() I toggle an attribute of channel boolean selected and then I change the background. I'm doing this only onClick() thats why I don't get why it's actuelly happening on other entries too. One thing I notices is: It seems to be only the "drawing"-part because the item which get selected "by it self" has still the selected value on false I think it seems to have something to do with the reuse of the views in the custom ListAdapters getView(...) Code of onClick() in ListActivity: @Override protected ViewHolder createHolder(View v) { // createHolder will be called only as long, as the ListView is not // filled TextView title = (TextView) v .findViewById(R.id.tv_title_channel_list_adapter); TextView content = (TextView) v .findViewById(R.id.tv_content_channel_list_adapter); ImageView icon = (ImageView) v .findViewById(R.id.icon_channel_list_adapter); if (title == null || content == null || icon == null) { Log.e("ERROR on findViewById", "Couldn't find Title, Content or Icon"); } ViewHolder mvh = new MyViewHolder(title, content, icon); // We make the views become clickable // so, it is not necessary to use the android:clickable attribute in // XML v.setOnClickListener(new ChannelListAdapter.OnClickListener(mvh) { public void onClick(View v, ViewHolder viewHolder) { // we toggle the enabled state and also switch the the // background MyViewHolder mvh = (MyViewHolder) viewHolder; Channel ch = (Channel) mvh.data; ch.setSelected(!ch.getSelected()); // toggle if (ch.getSelected()) { v.setBackgroundResource(R.drawable.row_blue_selected); } else { v.setBackgroundResource(R.drawable.row_blue); } // TESTING Log.d("onClick() Channel", "onClick() Channel: " + ch.getTitle() + " selected: " + ch.getSelected()); } }); return mvh; } Code of getView(...): @Override public View getView(int position, View view, ViewGroup parent) { ViewHolder holder; // When view is not null, we can reuse it directly, there is no need // to reinflate it. // We only inflate a new View when the view supplied by ListView is // null. if (view == null) { view = mInflater.inflate(mViewId, null); // call own implementation holder = createHolder(view); // TEST // we set the holder as tag view.setTag(holder); } else { // get holder back...much faster than inflate holder = (ViewHolder) view.getTag(); } // we must update the object's reference holder.data = getItem(position); // call the own implementation bindHolder(holder); return view; } I really would appreciate any idea how to solve this! :) If more information is needed please tell me. Thanks in advance!

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  • Move 3 rectangles up in their X but keep order of rectangles

    - by Nicolas Martel
    I have 3 rectangles being rendered here. Let's say i wanted to move them all above the line yet keep their order, how would i go about that? I tried subtracting the Y and height rather than adding the Y it but as expected, the lower rectangle goes at the top, middle stays in the middle and top goes to the bottom before: after: So is there any simple solution to render them just above rather than having to change all values ?

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  • JSF, How to set a property in a different page/backing bean and then navigate to that page?

    - by kgrad
    I am using JSF 2.0 and attempting to pass values between different pages in my App. The setup is as follows: I have a page called userSelect that has a backing bean userSelectBacking. On this page I display a list of users that can be selected and submit using an h:commandbutton, when the page is submit the navigation goes to a userEdit page. I have a page called userEdit, that has a backing bean userEditBacking which displays the information for a user and allows that user to be edited. I would like to pass the user selected from the userSelect page into the userEdit page. I am currently using f:setPropertyActionListener to set the user in my userEdit backing from the userSelect page, however when I navigate to the userEdit page, it loses the information I set. is there a way that I can pass the values between the two pages/backing beans? thanks

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  • JSF 2.0 method invocation with argument from var of dataGrid

    - by little_b
    Hello I use primefaces with facelets and i have a quastion: for example i have dataGrid and i want to call method of bean, that registered in faces-config, to include some dynamic content: <p:dataGrid var="provider" value="#{paymentFormBean.providers}"> <ui:include src="contentFactory.getSpecificForm('some attribute')"/> </p:dataGrid> How could i invoke getSpecificForm method with argument from var of dataGrid? Something like: <p:dataGrid var="provider" value="#{paymentFormBean.providers}"> <ui:include src="contentFactory.getSpecificForm(provider.formName)"/> </p:dataGrid> Could anyone help me? Thank you

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  • Question about decorator pattern and the abstract decorator class?

    - by es11
    This question was asked already here, but rather than answering the specific question, descriptions of how the decorator pattern works were given instead. I'd like to ask it again because the answer is not immediately evident to me just by reading how the decorator pattern works (I've read the wikipedia article and the section in the book Head First Design Patterns). Basically, I want to know why an abstract decorator class must be created which implements (or extends) some interface (or abstract class). Why can't all the new "decorated classes" simply implement (or extend) the base abstract object themselves (instead of extending the abstract decorator class)? To make this more concrete I'll use the example from the design patterns book dealing with coffee beverages: There is an abstract component class called Beverage Simple beverage types such as HouseBlend simply extend Beverage To decorate beverage, an abstract CondimentDecorator class is created which extends Beverage and has an instance of Beverage Say we want to add a "milk" condiment, a class Milk is created which extends CondimentDecorator I'd like to understand why we needed the CondimentDecorator class and why the class Milk couldn't have simply extended the Beverage class itself and been passed an instance of Beverage in its constructor. Hopefully this is clear...if not I'd simply like to know why is the abstract decorator class necessary for this pattern? Thanks. Edit: I tried to implement this, omitting the abstract decorator class, and it seems to still work. Is this abstract class present in all descriptions of this pattern simply because it provides a standard interface for all of the new decorated classes?

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